Interior Permanent Magnet (IPM) machines include a rotor assembly having a plurality of magnets of alternating polarity disposed around an outer periphery of the rotor assembly. The rotor assembly is rotatable within a stator which includes a plurality of windings. The rotor assembly magnetically interacts with the stator to generate rotation of the rotor assembly about a central axis of rotation.
An IPM machine may use either ferrite magnets or rare earth magnets, such as NdFeB. Ferrite magnets are less expensive, but produce a lower performance compared to rare earth magnets when utilized in identically configured IPM machines. Rare earth magnets typically used in IPM machines often include a heavy rare earth element, such as dysprosium or terbium, for operating temperature stability. Rare earth magnets that do not include the heavy rare earth elements have a significantly lower coercivity than rare earth magnets that do include the heavy rare earth elements, which makes them more susceptible to demagnetization. However, the inclusion of the heavy rare earth elements in the rare earth magnets increases the cost of the rare earth magnets.